مدیریت حشرات آفت بر پایه مواد فرار گیاهی در کشاورزی ارگانیک

ABSTRACT Plant Volatiles-based Insect Pest Management in Organic Farming

Promoted early in the 1940s by J. I. Rodale, and spurred by writings of British agriculturalist Sir Albert Howard, organic farming in the U.S. has been politicized and polarizing, despite growing popularity and consumer demand. Organically grown produce is an alternative to conventionally grown produce. Although sometimes difficult to verify scientifically (Dangour et al., 2009; Woese et al., 1999), organic products are often perceived by consumers as healthier and more environmentally friendly (Yue and Tong, 2009; Williams and Hammitt, 2001; Thompson and Kidwell, 1998).

The movement of organic farming in the U.S. was directly related to the indiscriminate use of chemical pesticides, herbicides, and fertilizers. Heavy reliance on synthetic agrochemicals, although undeniably an important factor contributing to increased food production and subsequent food security, led to significant health and environmental concerns. Despite reluctance of certain agricultural communities, organic agriculture gradually began to gain a foothold in U.S. culture. In 1979, the California Organic Food Act was signed into law, which established standardized production practices for organic food products.

In 1990, the Federal Organic Foods Production Act was passed, which established national standards for organic products, thus allowed for consistency in interstate trade. It took twelve years from that date to finalize a set of standards administered by the USDA’s National Organic Program. Since 2002, foods that are certified organic are accompanied by the USDA organic label. The USDA currently defines organic agriculture as “an ecological production management system that promotes and enhances biodiversity, biological cycles and soil biological activity. It is based on minimal use of off-farm inputs and on management practices that restore, maintain and enhance ecological harmony.” Since the adoption of national standards, organic sales in the U.S. have increased by 20% or more per year, representing one of the fastest growing sectors in agriculture (Oberholtzer et al., 2007). In a survey of organic farmers administered by the Organic Farming Research Foundation, farmers identified several major challenges faced by organic producers. Among these were issues related to practical weed management, followed by management of insect pests, vertebrate pests, and diseases (Walz, 1999). In this review, we restrict our discussion to management of insect pests. Among the key insect pests of concern, the most significant challenges come from cucumber beetles, flea beetles, Colorado potato beetles, aphids, codling moth, leafhoppers, and grasshoppers (Walz, 1999). These insect pests can cause significant losses in crop yield and produce aesthetics, especially in organic production systems. For example, despite implementation of various organic management efforts, codling moth larvae caused damage levels exceeding 25% in organic apple orchards in British Columbia (Judd et al., 1997). It is important to recognize that insects can cause differing levels of crop damage depending upon both the life stage of the insect pest and the developmental stage of the crop. In addition to direct feeding damage, insects can vector many different plant viruses. Wounds caused by insect feeding also become potential entry points for pathogenic fungi and bacteria. Therefore, adequate management of key insect pests remains critical to the health of organically grown crops and longevity of perennial plants within an organic production system. Undoubtedly, insect pests are an important factor in yield and commercial salability of conventional agricultural commodities.

Various management strategies have been developed to control insects, including botanical, biorational and synthetic insecticides as well as creation of transgenic pest- and disease-resistant crops, such as Bt corn and cotton. Genetically modified crops are not permitted for use in organic farming systems, and options of chemical insecticide are limited. In light of these constraints, it can be significantly more challenging to sufficiently manage insect pests using approved organic options. In this review, we first discuss approaches currently used to manage insect pest populations in organic production systems. We then review and discuss the potential for volatile compounds produced by plants to optimize or improve insect pest management in organic production.